This invention relates to active heating methods to provide a more comfortable cold weather sleeping environment for individuals participating in outdoor activities such as backpacking, hunting, camping, etc., and more particularly, to a novel and unique fluid heat transfer system for supplying heat to the type of foam or inflatable ground pad typically used under a sleeping bag for camping.
The use of fluid heat transfer to regulate the temperature of a bed is well known in the prior art. The general implementation of this method in a typical embodiment consists of an external heating system and a water circulation system which carries the heated water through tubing embedded within a mattress. A number of unique devices using these basic principles have been disclosed in the prior art, much of which dates back to the 1800's and early 1900's. These inventions were generally intended for fixed-place, in-door use, and as such, do not appear to be in great demand today where simple and efficient home heating is no longer a problem. This is evident even for the most recent inventions such as described by U.S. Pat. No. 3,438,069, issued to Long on Apr. 15, 1969, and No. 4,242,766, issued to Allegro on Jan. 6, 1981.
People familiar with outdoor activities such as backpacking, hunting, etc., which may involve camping outdoors, realize that even moderately cold temperatures can become a formidable problem, even when compensated for by warm clothing and well insulated sleeping gear. This is simply because it is very difficult to control the ambient temperature inside a thin-walled, non-insulated enclosure, such as a tent. Although a number of products such as kerosene or propane powered radiant heaters have been developed to mitigate this problem, these devices are generally cumbersome, inefficient, and dangerous due to the potential fire and asphixiation hazards they create. Furthermore, the radiant heat generated by such devices is insufficient to appreciably raise the surrounding ground temperature, and consequently does nothing to reduce the conductive loss of body heat to the surface beneath the sleeping bag. Existing portable foam and inflatable ground pads are designed to reduce conductive heat loss strictly by virtue of their insulating properties, and are therefore only partially effective in this regard.
It is therefore a main object of the present invention to provide a heating capability incorporated into a standard, backpack-transportable, sleeping bag ground pad.
Another object is to provide a sleeping bag heating system which is sufficiently compact and light such that it is totally portable within the general shape and volume of the basic ground pad while adding no more than a few pounds of extra weight to a backpack on which it is carried.
Still another object is to provide a sleeping bag heating system which is completely safe, and extremely simple and quick to assemble and operate in any outdoor environment.
Other objects will in part be obvious and will in part appear hereinafter.